The invention relates to a ring spinning or ring twisting machine, each of the spindles of which has an asynchronous motor for drive purposes and having auxiliary apparatus that are driven by at least one electric motor with a variable rotational speed, whereby the asynchronous motors which individually drive the spindles are connected to a primary converter and the electric motor driving the auxiliary apparatus is connected to an auxiliary converter; a control device is provided that controls both converters such that the ratio of the rotational speeds of the electric motor driving the auxiliary apparatus and the asynchronous motors remains constant.
With machines of this type it has proven necessary to drive the auxiliary apparatus, which in a ring spinning machine is the drawing equipment, by means of a synchronous motor, in order to retain the ratio of the rotational speeds of the auxiliary apparatus and the spindles constant, both during operation and during the start up and shut down procedures. This is a prerequisite for a uniform yarn quality. The primary disadvantage thereby is that during both start up and shut down procedures, care must be taken that the synchronous motor does not get out of step, and that if it does get out of step special measures must be taken in order to bring it back into synchronization.